Sulfur-containing compounds, nitrogen-containing compounds, oxygen-containing compounds, and the like are contained in crude petroleum as impurities and these impurities are also contained in distillate petroleum fractions obtained by distilling the crude petroleum. The impurities in these distillate petroleum fractions are reduced in their contents by a step of bringing the fractions into contact with a catalyst having a hydrogenation activity in the presence of hydrogen, the step being referred to as hydrotreatment. Especially, desulfurization for reducing contents of the sulfur-containing compounds is well known. Recently, from the viewpoint of reducing environmental load, there has been stricter demand for controlling or reducing contents of the impurities including the sulfur-containing compounds in petroleum products, and a large number of petroleum products referred to as so-called “sulfur free” are manufactured.
After a hydrotreating catalyst used for hydrotreatment of the distillate petroleum fraction is used for a certain period of time, its activity lowers due to deposition of coke or sulfur components, and the like, and therefore, replacement is carried out. Especially, the “sulfur free” is required, and a greater hydrotreating capability is required in hydrotreating facilities for fractions such as kerosene, gas oil, and vacuum gas oil. As a result, frequency of the replacement of the catalyst is increased, which leads to an increase in catalyst cost and an increase in an amount of waste catalyst.
To combat this, a regenerated catalyst (regenerated hydrotreating catalyst) regenerated from a spent hydrotreating catalyst is partially used in these facilities (For example, see Patent Literatures 1 and 2).